[chubes4]

Deletes the OpenCode runtime. Pi is now the only runtime wp-coding-agents installs or configures. Closes #846 (slice 4 of #751); Homeboy Cook already dropped its opencode backend (Extra-Chill/homeboy#15932).

Removed

• runtimes/opencode.sh, runtimes/opencode/ (including claude-code-auth.ts), and the OpenCode subagent projection
• opencode.json drift/repair (lib/repair-opencode-json.py, --repair-opencode-json, the additive repair phase), and the "Installing OpenCode" phase
• --runtime (passing it now errors with a pointer to Simplify to one runtime: Pi + composed AGENTS.md, Roadie as the managed surface #751), plus RUNTIME / DETECTED_RUNTIMES / AVAILABLE_RUNTIMES. A runtime key recorded in an installation profile is ignored. The setup profile compiler resolves auto to pi and rejects opencode.
• Roadie's OpenCode fallback: if Pi cannot be installed or verified, setup/upgrade now fails loudly instead of rendering a unit with no backend
• ~/.opencode/bin from the rendered Roadie PATH
• OpenCode-only tests and CI steps (including npm install -g opencode-ai)

Kept on purpose

• Kimaki-to-Roadie account import (roadie credentials import-opencode). It is a one-time data migration that reads Kimaki's OpenCode-format logins into the Roadie pool. Without it, a migrating Kimaki host would lose its logins.
• Composed AGENTS.md and the CLAUDE.md symlink are unchanged.
• Existing opencode.json / ~/.config/opencode on hosts are left alone. The installer just stops managing them.

Verification

• Full tests/*.sh suite plus node tests/setup-profile-compiler.mjs: no regressions against origin/main. Six tests also fail on clean main on this host (agents-md-guidance, cli-channel-binary-path, datamachine-worker, homeboy-service-identity, roadie-kimaki-migration, workspace-materialization); all pass in CI.
• Tests that render the Roadie unit use a stub Pi, so CI no longer depends on a real Pi on the runner.
• CI is green.

Removed flags

setup.sh / upgrade.sh --runtime and --repair-opencode-json are gone.

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AI assistance: implemented by Homeboy Cook (Pi, gpt-6.1-sol via roadie/cook-heavy) over three rounds. chubes-bot (Pi, Claude) scoped the work, triaged regressions against main, fixed the last roadie-accounts assertion, and verified the result.